From bc62bf8519f9005df2fb29dbd3d330202b258b6b Mon Sep 17 00:00:00 2001
From: Karl Williamson <khw@cpan.org>
Date: Sat, 1 Jun 2019 14:39:55 -0600
Subject: Add some defensive coding to av_store()

Don't decrement the reference count of the element about to be stored
into.

Likely, this is an error in the caller, but doing this action blindly is
like shooting yourself in the foot.  The branch prediction also added
ensures this shouldn't slow things down.

See http://nntp.perl.org/group/perl.perl5.porters/254974
---
 av.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

(limited to 'av.c')

diff --git a/av.c b/av.c
index 918844c376..f10f1247f4 100644
--- a/av.c
+++ b/av.c
@@ -356,8 +356,8 @@ Perl_av_store(pTHX_ AV *av, SSize_t key, SV *val)
 	}
 	AvFILLp(av) = key;
     }
-    else if (AvREAL(av))
-	SvREFCNT_dec(ary[key]);
+    else if (AvREAL(av) && LIKELY(ary[key] != val))
+        SvREFCNT_dec(ary[key]);
     ary[key] = val;
     if (SvSMAGICAL(av)) {
 	const MAGIC *mg = SvMAGIC(av);
-- 
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